A CLOSER LOOK AT THE INSULATION PRICE FACTORS*
Home insulation is a building product typically purchased once to serve for many years. However, its initial cost might appear to be somewhat expensive, considering the materials used in its production. So, what contributes to its price? Why is it so expensive? In this article, we will strive to answer these and other questions. By reading this article, you will also learn about the general cost of home insulation in the UK, the expenses for insulating a loft, the price per square metre of insulation, and the cost of exterior home insulation itself.
IS IT WORTH IT TO INSULATE YOUR HOUSE?
Indeed, it is commonly said that it is more cost-effective to retain the produced heat rather than constantly generating it. The same principle applies to UK homes. By insulating a house, we create a physical barrier for heat, effectively trapping it inside the rooms. As a result, the radiators or underfloor heating system don't need to produce as much heat to achieve the desired temperature of 22°C . This reduction in the demand for natural gas lowers the gas bills significantly.
An uninsulated home can be compared to a cup of hot tea. Imagine drinking tea from a styrofoam cup – the tea stays warm for a much longer period. That's why all takeaway shops are serving hot drinks in insulated cups. Similarly, our home's walls and roof play a crucial role. By insulating these critical areas, we ensure significant long-term savings.
Therefore, it is highly beneficial to insulate a home.
Retaining heat inside the house for just 4 hours can result in savings of around 17%, which is much higher than the current inflation rate. By investing in proper insulation, homeowners can enjoy these savings for years to come.
WHY IS INSULATION SO EXPENSIVE?
If you've already decided on home insulation, you may be wondering why insulation is so expensive. The more so, the materials used for insulation are often of natural origin.
The main reason for the high cost of home insulation is the expensive extraction and transportation of raw materials such as rock or oil. Further processing in the factory adds additional significant costs, as it involves expensive gas and electricity prices, as well as high wages for workers. Additionally, there are costs related to packaging, marketing, and ultimately distribution throughout the country. Moreover, the technological process of production often requires the use of high temperatures, not to mention the very high costs of the necessary machinery.
WHAT IS THE MOST COST EFFECTIVE WAY TO INSULATE A HOUSE?
The cheapest way to insulate a house internally is to insulate its upper parts using glass wool, and less commonly, rock wool. This is the fastest and most economical method of house insulation, especially for a small budget.
Another option at affordable price is to insulate the house with PIR boards, which have a thermal conductivity level of 0.022 W/mK, ranking second best in the UK market after phenolic boards from companies like Kingspan or Xtratherm (0.018-0.019W/mK)
Furthermore, the cheapest way to insulate a house externally is by using EPS (Expanded Polystyrene) together with a thin coat render system, also known as External Wall Insulation System. Applying EPS boards on the outer walls not only saves space inside the house but also eliminates the need for interior renovation work. Therefore, it can be concluded that external house insulation is less invasive.
While EPS (Expanded Polystyrene) may not have as low thermal conductivity as PIR or Phenolic boards, it performs excellently in atmospheric conditions. Investing in and using EPS with a thickness of 50mm and thermal conductivity of 0.032W/mK should pay off within the next 7-10 years. Its cost-effectiveness, combined with its durability and performance in various weather conditions, makes it a practical choice for external house insulation.
HOW MUCH DOES IT COST TO INSULATE A LOFT UK
Loft insulation is the most popular choice for homeowners in the UK when it comes to insulating their homes, and for good reason. As we remember from school, heat always rises, which means that the upper parts of a house experience the most significant heat losses. This is especially true for the loft. Poor insulation in the loft results in constantly working heating systems, leading to unnecessary costs, making it essential to eliminate this issue. However, the question arises: how much does loft insulation cost in the UK? Is it a time-consuming process that requires specialised knowledge? Not necessarily.
When insulating your loft with mineral wool, you should expect costs ranging from £4 to £12 per square metre. Taking into account the average size of a loft in the UK, which is around 35m2, you can quickly calculate that the insulation material itself would cost approximately £280. Additionally, you need to factor in installation costs, often amounting to double the value of the insulation material, which is around £500. By choosing the most affordable insulation, such as mineral wool, you should be able to stay within a budget of less than £1000.
Considering the price range for installation services in different cities across the UK, a very competitive price would be around £700 to insulate your loft.
HOW MUCH DOES IT COST TO INSULATE A HOUSE UK
When insulating a house, we should adhere to a general principle, which is to insulate every part of it. To put this into perspective imagine wrapping a Christmas gift. We need to insulate the bottom of the gift (the house's foundation), the sides of the gift (the walls of the house), and the top of the gift (the house's roof).
In general, this is how proper house insulation should look like in the UK. Specifically, you should insulate the foundations, the floor under wooden beams, the external walls, the loft, and the roof of the house. To achieve effective insulation, all of these areas should be properly insulated. If we skip insulating any of them, we might end up insulating the rest of the house unnecessarily. To find out how much house insulation costs in the UK, we need to assume that we are insulating all the components.
Taking into account the average size of a house in the UK, the costs can be estimated as follows: £5000-£6000 for external wall insulation (EWI), £2000-£3500 for the floor, around £1000 for the loft, and approximately £4500 for the roof. As seen above, this gives us a total of just below £15000. This is the aprox. sum that we should expect to pay when insulating a house in the UK.
INSULATION COST PER M2 UK
The cost of insulation in the UK depends on the material used. For instance, when using 100mm thick expanded polystyrene (EPS) insulation, you should expect costs around £19 per m2. A material four times stronger, XPS (extruded polystyrene) insulation, at the same thickness, has a cost of approximately £26 per m2.
The most commonly chosen insulation material in the UK is PIR, such as Celotex or Xtratherm (Unilin), which costs around £23 per m2 for a 100mm thickness. The most expensive insulation material is Phenolic board, which costs £38 per m2. On the other hand, the cheapest insulation material is glass mineral wool, with prices ranging from £8 to £10 per m2. To find out more on best insulation boards click here.
HOME INSULATION COST CALCULATOR UK
If you want to calculate how much insulation material you need to insulate your house and how much it will cost, we have already discussed it in the article: SAVE ON ENERGY BILLS - HOW TO CALCULATE THE AMOUNT OF INSULATION NEEDED TO COVER A SURFACE IN SQUARE METRES?
CAVITY WALL INSULATION COST
Cavity walls are frequently found in houses constructed after 1920. Cavity wall, as it is commonly referred to, is a wall that has insulation built into its cavity. Its cost can vary depending on the chosen method of installation. There are two main methods: partial fill installation, where a 50mm gap is left, and full fill intallation, where the gap between the two walls is completely filled with insulation.
Consequently, the cost of insulating a cavity wall can differ significantly based on the selected installation method. This is because different insulation thicknesses are used for partial fill and full fill. Considering only the 50mm gap in the partial fill method, it is evident that full fill insulation is twice as expensive due to the required thickness of the material.
Cost Comparison
Let's assume that for a specific cavity wall area, the cost of partial fill insulation is £800. This is because the partial fill method requires less insulation material, as it only fills part of the cavity.
Now, for the same area, the cost of full fill insulation might be £1900. Since full fill requires more insulation material to completely fill the cavity, it is more expensive compared to partial fill.
These examples highlight that the choice between partial fill and full fill insulation will not only impact the thermal efficiency of the wall but also affect the overall cost of the insulation. Homeowners and builders should consider these factors when deciding which method to use for cavity wall insulation.
The average cost of filling a cavity with partial fill insulation such as 50mm Xtratherm XT/CW is estimated to be around £18/m2 while the cost of filling the wall with full fill insulation such as 100mm Xtratherm CT/PIR CavityTherm is a maximum of £62/m2.
EXTERNAL WALL INSULATION COST UK
External insulation is accomplished by affixing an insulation layer to the external surface of the wall through mechanical fixings and adhesive. This insulation layer is then shielded with protective coatings of render or cladding.
When choosing this external wall insulation method, you should be prepared for additional costs, such as renting scaffolding, which is not cheap. The rental price for standard 10m high scaffolding is slightly over £700 (7 days), which is a considerable expense. However, for a well-organised installation company consisting of 3-4 people, a week should be sufficient to insulate an average-sized house in the UK.
The costs of insulating an average-sized house also include the entire thin coat render system. The most commonly used insulation materials for this purpose are Grey Polystyrene, Kingaspan K5 Phenolic foam boards, or Rockwool DD slab.
The cheapest insulation option for an external wall insulation system is around £11/m2 (50mm grey polystyrene). Additionally, two rolls of reinforcing mesh, covering 50m2 each, are typically required, costing £90 per roll. To adhere the insulation, adhesive costing £25 for a 25kg bag is needed, covering approximately 5m2. For every 100m2 of surface area, about 20 bags are required, totaling around £500. Priming the wall before rendering is necessary, and the final thin coat renders itself, which often exceeds £125, and covers approximately 10m2.
In conclusion, the estimated cost for insulating external walls is approximately £2750-5000 per 100m2, depending on the chosen materials and the efficiency of the installation process.
CONCLUSION
While insulation may seem expensive at first, it is crucial to remember that investing in high-quality insulation can result in long-term savings by reducing energy consumption and lowering utility bills. Moreover, a properly insulated home provides greater comfort and contributes to a more sustainable environment by reducing greenhouse gas emissions.
When considering insulation for your property, it is essential to seek quotes from reputable contractors and carefully assess the cost-benefit ratio.
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